I am not sure how EU servers are populated, but I would assume after the data center (DC) split, a mirror image as to what happened for the NA DC's happened with EU DC's. Everyone that got put on the "new" Data center transferred back or found a new/old server to go to with friends or more populated. This, plus all of the returning players for ShB would sky rocket population for a while. While the queue's are a minor annoyance, SE can't force people off of a server so it really isn't an issue they could fix without overhauling the game's servers. On the flip side, people are coming back and new people are playing the game, this could in turn allow for SE to upgrade their servers sometime in the future when the resources become available to them.